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區塊鏈錢包開發，第三周總結 (貨幣精度計算超大數運算)

這周主要做了 ETH錢包：（1）錢包列表展示錢包價值（2）在錢包內發起一個Transation交易（3）獲取交易詳情

當前熱錢包部分，對于以上三個功能最大的需求功能，最大阻礙是精度問題和超大數的的基本運算

一.錢包價值展示

參考imToken, imToken主做ETH錢包三年多，相當專業，有太多的地方值得我們學習。

首頁部分頭部是錢包內主幣和代幣換算成實體貨幣數量的總價值，列表部分是當前錢包內主幣和選中代幣集合，展示了幣的圖標、名稱、數量、兌換成實體貨幣價值。

關鍵是數量這里：
ETH 有很多單位，基本使用統計如下：

單位Unit	以最小單位Wei為基準的進制(Wei 數量)	使用頻率
Wei	1 wei	經常
KWei	10 * 3 wei
MWei	10 * 6 wei
GWei	10 * 9 wei	經常
microether	10 * 12 wei
milliether	10 * 15 wei
ether	10 * 18 wei	經常

二需要運算的地方：

發起一筆轉賬時的進制轉換，和gas 費用。

Gas limit 是用戶愿意為執行某個操作或確認交易支付的最大Gas量（最少21,000）單位個（即對應的是ETH的個數）

計算花費應該 gas fee = Gas Limit * Gas Price

這個是給礦工的傭金

第一步就是把gas price 從Gwei 轉為 ETH 再 * limit

Gas Limit*Gas Price

eg: 1Gwei≈0.00000002 ETH，所以傭金最少為0.00000002*21000=0.00042ETH

（1）用戶輸入轉賬ETH個數單位：ether

和服務端約定上傳一律用最小單位，這里需要做一次進制轉換即：1 ether = 10 * 18 wei

如果交易稍大就會超過 iOS 中精度了，更別提運算了。因為有Web3 ，提供 BigDecimal方案處理超大數的精度處理,iOS 這邊，完全可以自己寫超大數的加減乘除，也可以選擇一些成熟的第三 ,這里我使用了一個框架web3swift

web3swift，完全支持在iOS 客戶端上實施冷錢包，并發起交易的整個過程通過 Infura 節點（測試/主網）。具體參考（1）上介紹

所以，上一篇文章，我使用trust keystore 能完成創建錢包，導入錢包，校驗錢包的操作。今天換成web3swift，主要是符合我的需求和持續化的迭代設計。

至此，超大數，精度浮點數運算進制轉換使用swift 框架 web3swift來解決

使用舉例：

//
//  FIREnterUnitManager.swift
//  AkeyWallet
//
//  Created by HF on 2018/7/14.
//  Copyright ? 2018年 Fir.im. All rights reserved.
//

import Foundation
import BigInt
import web3swift

@objc public class FIREnterUnitManager:NSObject {
 
    //從ETH 轉換為 Wei
    public static func getWeiBigStringFrom(ethString:String) throws -> String {
        let eth = Web3.Utils.parseToBigUInt(ethString, units: .eth);//當前是eth
        if (nil == eth) {
            return ""
        } else {
            let balString =  Web3.Utils.formatToEthereumUnits(eth!, toUnits: .wei, decimals: 0)
            return balString!
        }
    }
    //從wei 到 eth
    public static func getETHFrom(weiString:String) throws -> String {
        let weiBig = BigUInt(weiString);
        let balString =  Web3.Utils.formatToEthereumUnits(weiBig!, toUnits: .eth, decimals: 8)
        return balString!;
    }//從當前進制到wei
    public static func getWeiFromUnit(unitString:String,decimal:Int) throws -> String {
        let balance = Web3.Utils.parseToBigUInt(unitString, decimals: decimal)
        let balString =  Web3.Utils.formatToEthereumUnits(balance!, toUnits: .wei, decimals: 8)
        return balString!;
    }//wei乘法
    public static func getMultiWei(wei1:String,wei2:String) throws -> String {
        let weiBig1 = BigUInt(wei1);
        let weiBig2 = BigUInt(wei2);
        let wei = weiBig1! * weiBig2!;
        let balString =  Web3.Utils.formatToEthereumUnits(wei, toUnits: .wei, decimals: 8)
        return balString!;
    }
    //wei加法
    public func getSumWei(wei1:String,wei2:String) throws -> String {
        let weiBig1 = BigUInt(wei1);
        let weiBig2 = BigUInt(wei2);
        let wei = weiBig1! + weiBig2!;
        let balString =  Web3.Utils.formatToEthereumUnits(wei, toUnits: .wei, decimals: 8)
        return balString!;
    }}

（2）有一些非超大數，比如一些顯示，虛擬幣、實體幣，求和，匯率計算什么的，也可以選擇上面的方法算，但是我的風格是按需處理，不是超大數，就是正常的金融數據運算，自己寫了一個工具類。

正常的浮點經度進行金融數據運算，會丟精度。蘋果針對浮點型計算時存在精度計算誤差的問題，提供NSDecimalNumber的計算類。

參考（2），自己完善一下邊界處理

NSDecimalNumber 有 NSRoundingMode 類型，我使用四舍五入類型 NSRoundPlain ,請參考者按需處理。

//
//  NSDecimalNumber+FIRDeimalTool.h
//  AkeyWallet
//
//  Created by HF on 2018/7/15.
//  Copyright ? 2018年 Fir.im. All rights reserved.
//

#import <Foundation/Foundation.h>

typedef NS_ENUM(NSInteger, calculationType) {
    Add,
    Subtract,
    Multiply,
    Divide
};

@interface NSDecimalNumber (FIRDeimalTool)

//自定義加減乘除
+(NSDecimalNumber *)aDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber1 type:(calculationType)type anotherDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber2 andDecimalNumberHandler:(NSDecimalNumberHandler *)handler;

//小數比較
+(NSComparisonResult)aDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber1 compareAnotherDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber2;

/**
 小數位數保留

 @param str1 小數
 @param scale 保留位數
 @return 結果
 */
+(NSString *)stringWithDecimalNumber:(NSDecimalNumber *)str1 scale:(NSInteger)scale;

extern NSComparisonResult StrNumCompare(id str1,id str2);

extern NSDecimalNumber *handlerDecimalNumber(id strOrNum,NSRoundingMode mode,int scale);


extern NSComparisonResult FIRCompare(id strOrNum1,id strOrNum2);

//加減乘除
extern NSDecimalNumber *FIRAdd(id strOrNum1,id strOrNum2);
extern NSDecimalNumber *FIRSub(id strOrNum1,id strOrNum2);
extern NSDecimalNumber *FIRMul(id strOrNum1,id strOrNum2);
extern NSDecimalNumber *FIRDiv(id strOrNum1,id strOrNum2);
//比大小
extern NSDecimalNumber *FIRMin(id strOrNum1,id strOrNum2);
extern NSDecimalNumber *FIRMax(id strOrNum1,id strOrNum2);
//定義運算結果小數取舍模態
extern NSDecimalNumber *FIRAdd_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
extern NSDecimalNumber *FIRSub_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
extern NSDecimalNumber *FIRMul_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
extern NSDecimalNumber *FIRDiv_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
extern NSDecimalNumber *FIRMin_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
extern NSDecimalNumber *FIRMax_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale);
/**
 字符串小數舍去末尾0
 
 @param stringOrNumber 字符串小數/Number/decimalNumer
 @return 舍去末尾0
 */
+(NSString *)getStringDecimalWithoutEndZero:(id)stringOrNumber;

@end

//
//  NSDecimalNumber+FIRDeimalTool.m
//  AkeyWallet
//
//  Created by HF on 2018/7/15.
//  Copyright ? 2018年 Fir.im. All rights reserved.
//

#import "NSDecimalNumber+FIRDeimalTool.h"

@implementation NSDecimalNumber (FIRDeimalTool)

+(NSDecimalNumber *)aDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber1 type:(calculationType)type anotherDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber2 andDecimalNumberHandler:(NSDecimalNumberHandler *)handler{
    if (!stringOrNumber2 || !stringOrNumber1) {
        NSAssert(NO, @"輸入正確類型");
        return nil;
    }
    NSDecimalNumber *one;
    NSDecimalNumber *another;
    NSDecimalNumber *returnNum;
    if ([stringOrNumber1 isKindOfClass:[NSString class]]) {
        one = [NSDecimalNumber decimalNumberWithString:stringOrNumber1];
    }else if([stringOrNumber1 isKindOfClass:[NSDecimalNumber class]]){
        one = stringOrNumber1;
    }else if ([stringOrNumber1 isKindOfClass:[NSNumber class]]){
        one = [NSDecimalNumber decimalNumberWithDecimal:[stringOrNumber1 decimalValue]];
    }else{
        NSAssert(NO, @"輸入正確類型");
        return nil;
    }
    
    if ([stringOrNumber2 isKindOfClass:[NSString class]]) {
        another = [NSDecimalNumber decimalNumberWithString:stringOrNumber2];
    }else if([stringOrNumber2 isKindOfClass:[NSDecimalNumber class]]){
        another = stringOrNumber2;
    }else if ([stringOrNumber2 isKindOfClass:[NSNumber class]]){
        another = [NSDecimalNumber decimalNumberWithDecimal:[stringOrNumber2 decimalValue]];
    }else{
        NSAssert(NO, @"輸入正確類型");
        return nil;
    }
    //排除NaN
    if (isnan(one.doubleValue) || isinf(one.doubleValue)) one = [NSDecimalNumber decimalNumberWithString:@"0"];
    if (isnan(another.doubleValue) || isinf(another.doubleValue)) another = [NSDecimalNumber decimalNumberWithString:@"0"];
    //
    if (type == Add) {
        returnNum = [one decimalNumberByAdding:another];
    }else if (type == Subtract){
        returnNum  = [one decimalNumberBySubtracting:another];
    }else if (type == Multiply){
        returnNum = [one decimalNumberByMultiplyingBy:another];
    }else if (type == Divide){
        
        if ([NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:another compareAnotherDecimalNumberWithStringOrNumberOrDecimalNumber:@(0)] == 0) {
            returnNum = nil;
        }else
            returnNum = [one decimalNumberByDividingBy:another];
    }else{
        returnNum = nil;
    }
    if (returnNum) {
        if (handler) {
            return [returnNum decimalNumberByRoundingAccordingToBehavior:handler];
        }else{
            return returnNum;
        }
    }else{
        NSAssert(NO, @"輸入正確類型");
        return nil;
    }
}

+(NSComparisonResult)aDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber1 compareAnotherDecimalNumberWithStringOrNumberOrDecimalNumber:(id)stringOrNumber2{
    if (!stringOrNumber2 || !stringOrNumber1) {
        NSAssert(NO, @"輸入正確類型");
        return -404;
    }
    NSDecimalNumber *one;
    NSDecimalNumber *another;
    if ([stringOrNumber1 isKindOfClass:[NSString class]]) {
        one = [NSDecimalNumber decimalNumberWithString:stringOrNumber1];
    }else if([stringOrNumber1 isKindOfClass:[NSDecimalNumber class]]){
        one = stringOrNumber1;
    }else if ([stringOrNumber1 isKindOfClass:[NSNumber class]]){
        one = [NSDecimalNumber decimalNumberWithDecimal:[stringOrNumber1 decimalValue]];
    }else{
        NSAssert(NO, @"輸入正確類型");
        return -404;
    }
    
    if ([stringOrNumber2 isKindOfClass:[NSString class]]) {
        another = [NSDecimalNumber decimalNumberWithString:stringOrNumber2];
    }else if([stringOrNumber2 isKindOfClass:[NSDecimalNumber class]]){
        another = stringOrNumber2;
    }else if ([stringOrNumber2 isKindOfClass:[NSNumber class]]){
        another = [NSDecimalNumber decimalNumberWithDecimal:[stringOrNumber2 decimalValue]];
    }else{
        NSAssert(NO, @"輸入正確類型");
        return -404;
    }
    //排除NaN
    if (isnan(one.doubleValue) || isinf(one.doubleValue)) one = [NSDecimalNumber decimalNumberWithString:@"0"];
    if (isnan(another.doubleValue) || isinf(another.doubleValue)) another = [NSDecimalNumber decimalNumberWithString:@"0"];
    //
    return [one compare:another];
}

+(NSString *)stringWithDecimalNumber:(NSDecimalNumber *)str1 scale:(NSInteger)scale{
    if (!str1) {
        return @"";
    }
    NSString *str = [NSString stringWithFormat:@"%@",str1];
    if (str && str.length) {
        if ([str rangeOfString:@"."].length == 1) {//有小數點
            NSArray *arr = [str componentsSeparatedByString:@"."];
            if (scale > 0) {
                NSInteger count = [arr[1] length];
                for (NSInteger i = count; i<scale; i++) {
                    str = [str stringByAppendingString:@"0"];
                }
                return str;
            }else{
                return arr[0];
            }
        }else{//沒有小數點
            if ([str rangeOfString:@"."].length) {
                return @"";
            }
            if (scale > 0) {
                str = [str stringByAppendingString:@"."];
                for (int i = 0; i<scale; i++) {
                    str = [str stringByAppendingString:@"0"];
                }
                return str;
            }else{
                return str;
            }
        }
    }else{
        return @"";
    }
}

NSComparisonResult StrNumCompare(id str1,id str2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:str1 compareAnotherDecimalNumberWithStringOrNumberOrDecimalNumber:str2];
}

NSDecimalNumber *handlerDecimalNumber(id strOrNum,NSRoundingMode mode,int scale){
    if (!strOrNum || strOrNum == nil) {
        NSLog(@"輸入正確類型");
        return nil;
    }else{
        NSDecimalNumber *one;
        if ([strOrNum isKindOfClass:[NSString class]]) {
            one = [NSDecimalNumber decimalNumberWithString:strOrNum];
        }else if([strOrNum isKindOfClass:[NSDecimalNumber class]]){
            one = strOrNum;
        }else if ([strOrNum isKindOfClass:[NSNumber class]]){
            one = [NSDecimalNumber decimalNumberWithDecimal:[strOrNum decimalValue]];
        }else{
            NSLog(@"輸入正確的類型");
            return nil;
        }
        //排除NaN
        if (isnan(one.doubleValue) || isinf(one.doubleValue)) one = [NSDecimalNumber decimalNumberWithString:@"0"];
        //
        NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:mode scale:scale raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:NO];
        return  [one decimalNumberByRoundingAccordingToBehavior:handler];
    }
}


NSDecimalNumber *FIRAdd(id strOrNum1,id strOrNum2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum1 type:Add anotherDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum2 andDecimalNumberHandler:nil];
}

NSDecimalNumber *FIRSub(id strOrNum1,id strOrNum2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum1 type:Subtract anotherDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum2 andDecimalNumberHandler:nil];
}
NSDecimalNumber *FIRMul(id strOrNum1,id strOrNum2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum1 type:Multiply anotherDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum2 andDecimalNumberHandler:nil];
}

NSDecimalNumber *FIRDiv(id strOrNum1,id strOrNum2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum1 type:Divide anotherDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum2 andDecimalNumberHandler:nil];
}

NSComparisonResult FIRCompare(id strOrNum1,id strOrNum2){
    return [NSDecimalNumber aDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum1 compareAnotherDecimalNumberWithStringOrNumberOrDecimalNumber:strOrNum2];
}

NSDecimalNumber *FIRMin(id strOrNum1,id strOrNum2){
    return FIRCompare(strOrNum1, strOrNum2) > 0 ? strOrNum2 : strOrNum1;
}
NSDecimalNumber *FIRMax(id strOrNum1,id strOrNum2){
    return FIRCompare(strOrNum1, strOrNum2) > 0 ? strOrNum1 : strOrNum2;
}
NSDecimalNumber *FIRAdd_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRAdd(strOrNum1, strOrNum2), mode, scale);
}
NSDecimalNumber *FIRSub_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRSub(strOrNum1, strOrNum2), mode, scale);
}
NSDecimalNumber *FIRMul_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRMul(strOrNum1, strOrNum2), mode, scale);
}
NSDecimalNumber *FIRDiv_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRDiv(strOrNum1, strOrNum2), mode, scale);
}


NSDecimalNumber *FIRMin_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRMin(strOrNum1, strOrNum2), mode, scale);
}
NSDecimalNumber *FIRMax_handler(id strOrNum1,id strOrNum2,NSRoundingMode mode,int scale){
    return handlerDecimalNumber(FIRMax(strOrNum1, strOrNum2), mode, scale);
}

+(NSString *)getStringDecimalWithoutEndZero:(id)stringOrNumber
{
    NSDecimalNumber *num = FIRAdd(stringOrNumber, @"0");
    return [NSString stringWithFormat:@"%@",num];
}

@end

參考：

(1) https://github.com/BANKEX/web3swift

(2)https://github.com/CodeJCSON/NSDecimalNumber

待續

posted on 2018-07-17 23:20 ACM_Someone like you 閱讀(880) 評論(0) 收藏舉報

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ACM_Someone like you

區塊鏈錢包開發，第三周總結 (貨幣精度計算超大數運算)

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ACM_Someone like you

區塊鏈錢包開發，第三周總結 (貨幣精度計算 超大數運算)

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區塊鏈錢包開發，第三周總結 (貨幣精度計算超大數運算)